Studies on Indole Hydroxylase

IV. Indole Hydroxylase and Aniline Hydroxylase

Abstract

1. Aniline hydroxylase had an optimum at pH 7.8, while that of indole hydroxylase was at pH 6.4.
2. Indole hydroxylase was less stable than aniline hydroxylase on storage.
3. In rabbit and hamster liver, indole hydroxylase was more active than aniline hydroxylase, while in guinea pig and mouse liver aniline hydroxylase was more active.
4. The degree of increase in enzyme activity after administration of methylcholanthrene differed for the two hydroxylases.
5. o-Phenanthroline strongly inhibited the hydroxylation of IBA while EDTA and KCN, which only inhibited the hydroxylation of IBA slightly, strongly inhibited that of aniline.
6. The activity of indole hydroxylase apparently decreased more than of aniline in regenerating liver.
7. It is concluded that indole hydroxylase and aniline hydroxylase are different enzymes. Indole hydroxylase is specific for indole compounds.